def A(a, b):
    return a + b
def B(a, b):
    return a - b
def C(a, b):
    return a * b
def D(a, b):
    if b == 0:
        return "错误：除数不能为0"
    return a / b

def P():
    print("简易计算器")
    print("1. 加法")
    print("2. 减法")
    print("3. 乘法")
    print("4. 除法")
    a = int(input("请选择操作："))
    b = float(input("请输入第一个数："))
    c = float(input("请输入第二个数："))

    if a == 1:
        print(f"结果：{A(b, c)}")
    elif a == 2:
        print(f"结果：{B(b, c)}")
    elif a == 3:
        print(f"结果：{C(b, c)}")
    elif a == 4:
        d = D(b, c)
        print(f"结果：{d}")
    else:
        print("无效选择")
P()